When we think about making a simple measurement, such as an outside diameter, many methods can be used. These would include calipers, micrometers, mechanical snap gauges, air snaps, CMMs, and special fixture gauges, just to mention a few.

The problem with all these methods is that, while each is good in its own right, there may be a bias seen among them. Each method has some slight variations that can cause differences in results. It may be different gauging force, different process methods (such as the difference between contact and air gauging), or different measuring techniques, such as a CMM doing average diameters as opposed to a caliper using two-point measurements.

So, with all these techniques and potential pitfalls, how do you account for multiple measurements to be made by different personnel, in either the same or different locations, and then agree on the results? The bottom line is, you don’t. The only correct way is to determine an agreed-upon method for making the measurement and ensure that each location follows the same process.

 …